The capture of many electrons by Ar !7+ ions, at low velocity, near a metallic surface, has been studied. Multiexcited bound states with many electrons in the outermost shells (hollow atoms) have been observed. The surrounding of an ionic excited core by many outermost electrons greatly decreases the lifetimes of the states. This characteristic decrease explains the main striking features of the relaxation of the ions.

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The K x-ray spectrum arising from doubly JC-ionized gallium atoms has been studied by means of a coincidence experiment with two solid-state detectors. A new energy range in K x-ray spectra (hyper satellite range) is observed. Hyper satellite lines are shifted about 15 times more than the usual satellite lines. The if-satellite spectrum following KL -ionized states has also been studied.

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The n =2-• n = 1 lines of hydrogenlike and heliumlike uranium have been observed and are being reported for the first time. The spectrum consists of all allowed and forbidden lines. We have done a preliminary energy measurement of these lines with a precision in the (4-12) x 10 ~4 range.

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The hyperfine-quenched transition 2 3 /Vl 'So has been observed in heliumlike gadolinium (Gd 62+ ) in the two isotopes ,55 Gd and ,57 Gd. The lifetime for the transition (to) has been measured for each isotope and found to be r 0 (l55) = 13.43(27)x 10" l2 sec and r 0 (l57) =7.65(55)x 10" ,2 sec. From the measured lifetimes a value is inferred for the absolute value of the 2 3 Po-2 3 P\ fine-structuring splitting |A£o-i| in Gd 62+ with the result |AEo-i| = 18.57(19) eV, where the error represents 1 standard deviation. This result is compared with calculations based on the multiconfiguration Dirac-Fock method and on the unified method. PACS numbers: 32.30.Rj, 12.20.Fv, 31.30.Jv, 32.70.FwThe splittings of the I s Pj levels [l] in two-electron ions (AEJ.J) are determined largely by the electron-electron interaction. The measurement of these splittings constitutes, therefore, a test of theories of this interaction in the simplest atomic system in which it can be observed. Because of the rapid scaling of the relativistic part of this interaction with atomic number Z, measurements at high Z provide a particularly sensitive test of the relativistic theory. Calculations of the fine-structure splittings generally include the effects of relativity by a perturbation expansion in the parameter (Z«) 2 . The problems associated with this approach at high Z are illustrated by the fact that in ordinary helium (Z=2) the calculations [2] are accurate at the ppm level, whereas the most elaborate calculations [3,4] at Z=64 are accurate at only the few percent level. Accurate experimental measurements performed at high Z can therefore act to stimulate further theoretical work in including relativistic effects in the calculation of two-electron energy levels.Accurate experimental measurements of the two-electron fine-structure splittings in the I s Pj multiplet have been performed in He and Li + using radio-frequency spectroscopy [5] and laser spectroscopy [6]. The extension of laser spectroscopy to the heliumlike ion F 7+ was achieved by Myers et al.[7], who measured the interval 2 3 / > i-2 3 / > 2 (AE1.2). However, extension of the laser method to much higher Z is experimentally not feasible. Indirect measurements using x-ray and UV spectroscopy have been performed and are summarized in review articles by Martin [8] and Desequelles [9], but such measurements have not been very precise. So far there have been no measurements reported with sufficient precision to examine the theoretical predictions at high Z. In thisLetter we describe the first measurement at high Z with a precision smaller than the current theoretical accuracy.The measurement reported here is of the interval AEo.\ in the two-electron ion Gd 62+ . Gadolinium has a number of stable even-even isotopes with nuclear spin 7=0. For these isotopes, the radiative decay 2 3 /Vl '-So is strictly forbidden and the 2 3 / > o state undergoes E\ decay to the 2 3 S1 state with a calculated lifetime [10] of r(2 3 / > 0 ) =0.339xl0~9 sec. Gadolinium also has two stable isotopes ( ,55 ...

Grenoble Test Source (GTS) is a room temperature electron cyclotron resonance ion source whose purpose is to deepen the knowledge of this type of device. GTS was designed according to magnetic scaling laws determined with the SERSE source [Hitz et al., Rev. Sci. Instrum. 73, 509 (2002); Gammino et al., ibid. 72, 4090 (2001)] while keeping enough flexibility in terms of magnetic confinement and rf heating to determine best conditions for the production of intense beams of any charge state. First results were presented 1 year ago [Hitz et al., 8th European Particle Accelerator Conference, 2002; 15th International Workshop on ECR Ion Sources, 2002]. Since then, some improvements have been performed mostly in the magnetic confinement, beam extraction and analysis. Updated ion beam intensities are presented: e.g., 0.5 mA of Ar11+ at 18 GHz, 20 μA of Ar16+ and 1.8 μA of Ar17+ when GTS is operated at 14.5 GHz. On the other hand, charge coupled device imagers have been installed to diagnose and monitor the ion beam and some beam images are shown.